Hitherto, in the various display apparatuses such as liquid crystal display, plasma display, and CRT display, if external light of a fluorescent lamp or the like is reflected onto the surface, visibility is remarkably deteriorated. Therefore, there is used a method whereby a reflectance is decreased by forming an optical multilayer film or a film of a low refractive index onto the surface of the display apparatus or the external light is diffused and reflected by forming an optical film such as an anti-glare film having micro concave/convex portions on the surface, thereby blurring a reflection image.
However, there is such a problem that if the optical multilayer film is used, manufacturing costs increase, an anti-glare property is insufficient, and even if the manufacturing costs are suppressed by using the low refractive index film, the reflectance is relatively high, so that the user is aware of the reflection.
On the other hand, the method whereby the anti-glare film having the micro concave/convex portions on the surface is used and the reflection image is blurred by the diffuse reflection is widely used because it is reasonable and high productivity is obtained.
A construction of a conventional anti-glare film 101 is shown in FIG. 1. The anti-glare film 101 has: a substrate 111; and an anti-glare layer 112 formed on the substrate 111. The anti-glare layer 112 is formed by a resin containing fine particles 113 made of irregular silica or resin beads. By projecting the fine particles 113 from the surface of the anti-glare layer 112, micro concave/convex portions are formed on the surface. The anti-glare film 101 is formed by coating the substrate 111 with a coating material containing the fine particles 113, a resin, a solvent, and the like and hardening the coating material. According to the anti-glare film 101 having the construction mentioned above, since light which enters the anti-glare layer 112 is scattered by the micro concave/convex portions on the surface of the anti-glare layer 112, a reflection due to the surface reflection is reduced.
However, since the micro concave/convex portions on the surface of the anti-glare film 101 are formed by: the fine particles 113 projected from the surface; and a binder portion in which an interval between the projections of the fine particles 113 is formed by a continuous slope, although the film has a high anti-glare property, there is such a problem that the light which passes through the anti-glare layer 112 in the vertical direction is also strong scattered and transmitted image clarity deteriorates.
Therefore, as shown in FIG. 2, such a technique that a filling rate of the fine particles 13 in the anti-glare layer 112 is reduced and a cycle of the concave/convex portions on the surface of the anti-glare layer 112 is extended, thereby suppressing the deterioration in transmitted image clarity is considered. However, there is such a problem that if it is intended to realize the smooth concave/convex portions by extending the cycle of the concave/convex portions on the surface of the anti-glare layer 112 as mentioned above, flat portions are formed in the binder portions between the projections of the fine particles 113, so that the anti-glare property deteriorates.
Since there is a relation of trade-off between the anti-glare property and the transmitted image clarity as mentioned above, an anti-glare film in which the deterioration in transmitted image clarity is suppressed while having the anti-glare property is demanded. Particularly, the realization of the high fineness of the image display apparatus has been progressed in recent years. If the conventional anti-glare film is used, since problems such as generation of micro luminance variation which is what is called a glare (scintillation), reduction in contrast of a fine video image, and the like occur, an anti-glare process which can cope with the realization of high fineness and can improve those problems is demanded and various examinations are being progressed.
For example, techniques for improving the glare and clarity while keeping the anti-glare property by adjusting an internal scattering have been disclosed in the Official Gazettes of Japanese Patent Nos. 3507719 and 3515401. A technique for improving the glare by setting an average interval between the concave and convex portions of the anti-glare layer to be sufficiently narrower than a pixel size of the image display apparatus has been disclosed in the Official Gazettes of Japanese Patent No. 3661491.
However, since there is a relation of trade-off between the anti-glare property and the transmitted image clarity which exerts an influence on a contrast of the fine drawing image as mentioned above, it is difficult to improve the transmitted image clarity while maintaining the anti-glare property. According to the techniques disclosed in foregoing Patent Documents 1 to 3, although the anti-glare property and the transmitted image clarity can be improved to a certain extent, a degree of the improvement is insufficient and it is demanded to further improve both of those characteristics.
An object of the embodiment is to provide an optical film having an anti-glare property and having excellent transmitted image clarity and to provide a manufacturing method of such a film, an anti-glare polarizer using such a film, and a display apparatus using such a film.